Kahi Kai - Marine Life Infosheet

WHAT ARE PLANKTON?

Plankton are some of the most diverse and abundant organisms on the planet. The term plankton comes from the Greek word “planktos” meaning wanderer or drift- er. Hence, plankton describes organisms that live in the water and cannot swim against major currents. PLANKTON COME IN TWO TYPES 1. Phytoplankton (plant-like) Plant-like plankton are known as phytoplankton. Each phytoplankton is a single cell or a chain of cells. Phytoplankton are microscopic and do not look anything like plants that grow on land, they lack roots, stems, and leaves. But like terrestrial plants, they are able to capture sunlight and convert it into energy. This process, called photosynthesis, also makes the oxygen that we need to breath. Phytoplankton are extremely productive considering their small size - over a million phytoplankton can fit in a teaspoon of seawater. However, when conditions are just right, phytoplankton can grow in such large numbers that they are able to generate a bloom that can be seen from space.

2. Zooplankton (animal-like) Animal-like organisms that drift in the ocean are called zooplankton. Zooplank- ton are larger than phytoplankton, ranging from microscopic sizes to jellyfish that can grow to be several meters in length. Some large zooplankton can move under their own power, migrating towards the surface water at night to feed on phytoplankton or smaller zooplankton and sink- ing to deeper waters during the day to avoid being eaten by larger animals. There are two types of zooplankton: temporary and permanent. • Temporary zooplankton (meroplankton) only spend part of their life cycle as plankton. Certain meroplankton, such as crabs and fish, are plankton only when they are young larvae. When they grow up, they transform into completely different forms.

• Permanent zooplankton (holoplankton) spend their whole life as plankton. For example, copepods stay as zooplankton their entire lives and are considered the most abundant animals in the ocean.

Did You Know...

• Phytoplankton produce about 50% of the oxygen that we breathe every day. • The weight of all the plankton in the oceans is greater than that of all the fish, dolphins and whales put together. • Copepods (zooplankton) are said to be the richest source of protein in the ocean. WHY ARE PLANKTON IMPORTANT?

They Produce Oxygen We Breathe Phytoplankton are sometimes called the grasses of the sea because they produce around 50% of the oxygen in the atmosphere through photosynthesis. During photosynthesis, phytoplankton use the sun’s energy to combine carbon Everything is dioxide and water into simple foods. This process removes carbon dioxide from somehow linked seawater, which allows the water to absorb carbon dioxide produced in the at- to plankton and mosphere as well as produce at least half of the oxygen we breathe. it is important They are a Food Source for All that we protect our oceans so Plankton also serve as the nutritional basis for all animals that live in our that they can oceans.They are primary producers that provide the first form of energy within maintain their marine food webs (Fig. 1). natural balance. Phytoplankton are then consumed by zooplankton, which are known as primary consumers. These, in turn, become food for larger organisms such as bivalves, crustaceans, fish, and baleen whales. These fish and other animals then become food for animals near the top of the food chain, such as sharks, toothed WHAT CAN whales, and humans. Without plankton, none of the larger fish or animals in the ocean could survive; YOU DO? the entire marine food web would collapse. Sunlight

You can help protect plankton by: Small Fish

• Decreasing Tuna Plankton pollution Baleen whale • Using less energy Figure 1. Simplified food web of an open ocean ecosystem. Shark • Urging They Help the Oceans individuals and compa- Plankton play a role in the biogeochemical cycles of many important chemical nies to stop elements, including the ocean’s carbon cycle. destroying Some plankton play an important role in the disposal of sewage and in the natu- habitat on ral purification of polluted water. Interestingly, plankton can also indicate the land and in health of our oceans or the degree of pollution. the ocean The timing and production of plankton are dependent on water temperature and • Encouraging the availability of nutrients, which are normally well balanced and predictable others to stop throughout the seasons. overharvesting ocean wildlife The disturbance of one of these factors can have drastic effects on the plankton composition. Fertilizers used for agriculture can end up in the ocean and induce An important plankton blooms that are the consequence of a strong phytoplankton prolifera- part of saving tion, but to the detriment of other organisms. the ocean is Furthermore, several studies have shown that there exists a strong relationship working between larval survival and production of plankton. Therefore, changes in the together natural variation of plankton populations can affect fish populations. and educating

others. References: C-MORE, David Suzuki Foundation, Intech, National Geographic Society, NASA, NOAA, University of Rhode Island’s Office of Marine Programs, and University of Wisconsin Center for Limnology. 2013 © Kahi Kai (www.kahikai.org)